Conventionally, there is a hybrid integrated circuit device including two integrated circuit substrates that face each other, conducting paths having desired shapes formed on opposing main surfaces of the substrates, and a microcomputer that is connected to the conducting paths and that has a desired control function. The hybrid integrated circuit device further includes peripheral circuit elements to which a predetermined control output signal is fed from the microcomputer and that is connected to the conducting paths on the substrates, and an integrated case member disposed between the two substrates. A hole is formed in one of the substrates at a desired position and a wiring substrate on which the microcomputer is mounted is accommodated and is disposed in the space formed by the hole.
Incidentally, in the conventional hybrid integrated circuit device, since the two integrated circuit substrates are disposed so as to face each other, there is a great deal of space between the two integrated circuit substrates in which no circuit element and the like are disposed, and high density mounting is not sufficiently achieved.
The following is a reference document.    [Document 1] Japanese Laid-open Patent Publication No. 03-174757.